Oxidation-free casting apparatus for continuous casting

ABSTRACT

An oxidation-free casting apparatus for continuous casting using a ladle provided with a sliding gate. The lower nozzle of the ladle is surrounded by a steel hood and a skirt depending therefrom, with the free end of the skirt placed via a spacer, if necessary, or directly on the tundish lid, and an inert gas jet for spraying inert gas in directions substantially perpendicular and parallel to the liquid steel stream is disposed within the space enclosed by the hood and skirt.

United States Patent 11 1 Tozaki Nov. 25, 1975 OXIDATION-FREE CASTING APPARATUS FOR CONTINUOUS CASTJNG [75] Inventor:

[73] Assignee: Sumitomo Metal Industries, Ltd.,

Osaka, Japan 221 Filed: Nov. 11, 1974 21 Appl. No.: 522,948

Yasuyuki Tozaki, Kashima, Japan [30] Foreign Application Priority Data Nov. 12, 1973 Japan 48-129843[U] [52] US. Cl 164/259; 164/337 [51] Int. Cl. B22D 37/00 [58] Field of Search 164/66, 256, 259, 64, 120, 164/258, 281, 136, 155, 160, 244, 264, 304, 315, 337, 82; 266/34 V [56] References Cited UNITED STATES PATENTS 2,997,384 8/1961 Feichtinger 164/66 X Hornak 164/66 X Halliday 164/259 X Primary Examiner-Francis S. Husar Assistant Examiner-John S. Brown [57] ABSTRACT An oxidation-free casting apparatus -for continuous casting using a ladle provided with a sliding gate. The lower nozzle of the ladle is surrounded by a steel hood and a skirt depending therefrom, with the free end of the skirt placed via a spacer, if necessary, or directly on the tundish lid, and an inert gas jet for spraying inert gas in directions substantially perpendicular and parallel to the liquid steel stream is disposed within the space enclosed by the hood and skirt.

9 Claims, 4 Drawing Figures US Patent N0v.25, 1975 Sheet1of2 3,921,704

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US. Patent Nov.25, 1975 Sheet20f2 3,921,704

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FIG.2

FIG.4

OXIDATION-FREE CASTING, APPARATUS FOR CONTINUOUS CASTING This invention relates to an oxidation-free casting apparatus for continuous casting using a ladle provided with a sliding gate.

In the continuous casting process, the solidifying speed of the slab is high compared to the ordinary casting of ingots, and consequently a large quantity of nonmetallic conclusion is introduced into the slab and causes various defects of the product. The non-metallic products of dissolution of various refractory materials and oxides produced when the molt being cast is contacted by air, and its major proportion is constituted by the product of oxidation by air at the time of casting. In the continuous casting, the liquid steel is subject to oxidation by air between ladle and tundish and between tundish and mold. Between the tundish and mold the liquid steel can be isolated from atmosphere by using a submerged nozzle or by means of powder covering. In the case of using a ladle provided with a sliding gate, however, the submerged nozzle has not still been put to practical use between the ladle and tundish since it is likely to be choked or broken and also since it is difficult to provide space for installing desired shields because of the movement of the sliding gate.

An object of the invention is to provide an oxidationfree casting apparatus for continuous casting using a ladle provided with a sliding gate, in which apparatus the space between ladle and tundish perfectly isolated from atmosphere for perfectly preventing the oxidation by air in this region and which is particularly effective for a ladle of a large capacity of the order of 100 to 250 tons of liquid steel.

According to the invention, a steel hood and a skirt depending therefrom are provided to surround the lower nozzle of the ladle, with the free end of the skirt disposed to surround the opening of the tundish, and an inert gas jet for spraying inert gas in directions substantially perpendicular and parallel to the liquid steel stream is provided within the space enclosed by the hood and skirt.

With this construction according to the invention, the liquid steel flowing down from the ladle lower nozzle is surrounded by the shield constituted by the hood and skirt. The skirt depending from the hood may, for instance, consist of asbestos coated with aluminum, and includes a buried refractory heat insulator. Also, the lower end of the skirt is placed on a steel member of a desired contour, which is placed on top of the lid of the tundish and surrounds the opening thereof, thus perfectly isolating the liquid steel stream from atmosphere. In addition, the liquid steel stream is surrounded by inert gas sprayed from the inert gas jet disposed within the hood in directions perpendicular and parallel to the liquid steel stream, thereby to perfectly prevent the oxidation of the liquid steel. The skirt made of the heat insulating refractory material is used to the end of providing for movability with the movement of the sliding gate for perfectly isolating the liquid steel from atmosphere. The afore-mentioned steel member is provided, if it is found necessary, in order to prevent the splash against the free end of the skirt, thermal deterioration and combustion of the skirt free end with the heat of radiation and deterioration of the skirt cooling efficiency of the inert gas.

The above and other objects, features and advantages of the invention will become more apparent from the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a rough elevational sectional view of the apparatus according to the invention;

FIG. 2 is a fragmentary sectional view, to an enlarged scale, showing a modificationof the steel member provided to surround the tundish opening;

FIG. 3 is a view similar to FIG. 2 but showing another modification of the steel member; and

FIG. 4 is a fragmentary perspective view of a modification of the inert gas jet.

Referring now to the drawings, and particularly to FIG. 1, a ladle 1 has an opening 2 provided with an upper nozzle 3, which penetrates a stationary base. 4 secured to the ladle 1.

A sliding gate 5 is movable underand in frictional contact with the stationary base 4 and is operated by a cylinder 6. The sliding gate 5 has a nozzle holder 8 carrying a lower nozzle 7. Designated at 9 is a steel hood, which is secured by support means 10 to the holder 8. In the shut-off state of the sliding gate, the hood 9 and a skirt to be described hereinafter assume a position indicated by broken lines in FIG. 1. The hood 9 consists of a small diameter portion 11 having the same diameter as the outer diameter of the holder 8, a funnel portion 12 downwardly flaring from the small diameter portion 1 1 and a large diameter portion 13 having substantially the same diameter as the opening 18 of-a tundish 17. The small diameter portion 11, funnel portion 12 and large diameter portion 13 are integral with one another. l

The support means 10 is preferably simple in construction in view of the deformation and other effects of the heat of radiation upon the hood; for example, it may be pins inserted in holes formed in the hood and nozzle holder 8. s

Designated at 14 is a cylindrical skirt preferably made of asbestos coated with aluminum and depending from the large diameter portion 13 of the hood 9 such as to surround the liquid steel stream. Its upper end is secured by means of annealed steel wires to the hood, and it has a free lower end 16. The skirt also includes a buried heat insulator 15, for instance kaolin wood, which serves to prevent deterioration and combustion due to the heat of the liquid steel stream.

The free end 16 of the skirt 14 flares such as to surround the opening 18 of the tundish 17.

If desired, a steel member 20 of a U-shaped sectional profile as shown in FIG. 1 or an H-shaped sectional profile as shown in FIG. 2 or refractory bricks 21 as shown in FIG. 3 may be interposed between the free end 16 of the skirt and the lid 19 of the tundish 17.

Disposed along the inner wall of the large diameter portion 13 of the hood 9 are two annular inert gas jet tubes 22 and 23, which are secured by means of welding to the hood. The jet tube 22 has jet holes 24 for spraying inert gas in directions substantially perpendicular to the liquid steel stream, while the other jet tube 23 has jet holes 25 for spraying inert gas in a-direction substantially parallel to the liquid steel stream.

The inert gas jet tubes 22 and 23 are connected to a connection tube 26, which is in turn connected to a supply tube 27, and the inert gas is supplied therethrough under a pressure of 2 to 6 kg/cm". The inner diameter of the inert gas jet tubes 22 and 23 is 15 to 30 mm, the diameter of the jet holes is 1.5 to 5 mm, and the distance between adjacent jet holes is to mm.

The supply tube 27 which is commonly connected through the connection tube 26 to the inert gas jet tubes 22 and 23 may be replaced with, separate supply tubes individually connected to the respective inert gas jet tubes. Further, the jet tubes 22 and 23 themselves may be replaced with a single jet tube having jet holes 28 and 29 respectively directed perpendicular and parallel to the liquid steel stream as shown in FIG. 4.

This inert gas jet not only serves to fill the space surrounding the liquid steel stream with inert gas but also has the effect of cooling the skirt. 1

In order to examine the effect of the apparatus according to the invention over the prior-art apparatus strips were produced by rolling slabs cast from lowcarbon killed steel. With the apparatus according to the invention 98 first-grade strips were obtained per 100 strips, and only 2 second-grade strips resulted. On the other hand, with the prior-art apparatus only 5 firstgrade strips were obtained. (The first-grade strip is one which has no pits though it has visible slivers, and the second-grade strip is one which has both slivers and pits.)

As has been shown, according to the invention the liquid steel stream between the ladle and tundish in the continuous casting can be sealed from the atmosphere with the inert gas filling means whichis simple in construction and easy to operate, whereby the oxidation of the liquid steel by oxygen in the atmosphere can be prevented to prevent formation of oxides, particularly A1- 0 Thus, it is possible to produce pure slabs free from non-metallic contents, particularly flaws and specks in the slab for rolling can be greatly reduced. Also, steady and stable operation can be ensured without the possibility of choking of the submerged nozzle with A1 0 Furthermore, improved effect may be obtained by sealing between the tundish lid and the apparatus body with a seal member (such as asbestosrope) and spraying the inert gas from a slag cement pipe.

What is claimed is:

1. In combination with an oxidation-free casting apparatus for continuous casting having a ladle provided with a sliding gate, the improvement comprising a steel hood mounted on anozzle holder secured to the sliding gate, a skirt depending from the lower end of said hood, and an inert gas jet means consisting of at least one inert gas jet tube being disposed along the inner wall of said hood and having jet holes forspraying inert gas in directions substantially perpendicular and parallel to comprises a spacer means interposed between the free I end of said skirt and the lid of said tundish and placed on the lid of the tundish so as to surround the tundish opening.

3. The apparatus according to claim 2, wherein said spacer means consists of a steel member having a substantially U-shaped cross sectional profile. I

4. The apparatus according to claim 2, wherein said spacer means consists of a steel member having a substantially H-shaped cross sectional profile.

5. The apparatus according to claim 2, wherein said spacer means consists of refractory bricks.

6. The apparatus according to claim 1, wherein said skirt coated with aluminum includesa buried heat insulator of a refractory material such as kaolin wool.

7. The apparatus according to claim 1, wherein inert I gas is supplied to said inert gas jet tube under a pressure of 2 to 6 kg/cm 1 g 8. The apparatus according to claim 1, whereinthe diameter of said inert gas jet tube ranges between 15 and. 30 mm, the diameter of the jet holes ranges be tween 1.5 and 5 mm, and the distance between adjacent jet holes ranges between 10 and 20 mm.

9. The apparatus according to claim 1, wherein said hood consists of a small diameter portion with substan tially the same diameter as the outer diameter of said nozzle holder, a funnelportion downwardly flaring from said small diameter portion and a large diameter 7 portion depending from the lower end of said funnel portion and having substantially the same diameter as the diameter of the tundish opening, these portions another. 

1. In combination with an oxidation-free casting apparatus for continuous casting having a ladle provided with a sliding gate, the improvement comprising a steel hood mounted on a nozzle holder secured to the sliding gate, a skirt depending from the lower end of said hood, and an inert gas jet means consisting of at least one inert gas jet tube being disposed along the inner wall of said hood and having jet holes for spraying inert gas in directions substantially perpendicular and parallel to the longitudinal axis of said hood said skirt having a free end contoured so as to be adapted to surround the opening of a tundish.
 2. The apparatus according to claim 1, which further comprises a spacer means interposed between the free end of said skirt and the lid of said tundish and placed on the lid of the tundish so as to surround the tundish opening.
 3. The apparatus according to claim 2, wherein said spacer means consists of a steel member having a substantially U-shaped cross sectional profile.
 4. The apparatus according to claim 2, wherein said spacer means consists of a steel member having a substantially H-shaped cross sectional profile.
 5. The apparatus according to claim 2, wherein said spacer means consists of refractory bricks.
 6. The apparatus according to claim 1, wherein said skirt coated with aluminum includes a buried heat insulator of a refractory material such as kaolin wool.
 7. The apparatus according to claim 1, wherein inert gas is supplied to said inert gas jet tube under a pressure of 2 to 6 kg/cm2.
 8. The apparatus according to claim 1, wherein the diameter of said inert gas jet tube ranges between 15 and 30 mm, the diameter of the jet holes ranges between 1.5 and 5 mm, and the distance between adjacent jet holes ranges between 10 and 20 mm.
 9. The apparatus according to claim 1, wherein said hood consists of a smalL diameter portion with substantially the same diameter as the outer diameter of said nozzle holder, a funnel portion downwardly flaring from said small diameter portion and a large diameter portion depending from the lower end of said funnel portion and having substantially the same diameter as the diameter of the tundish opening, these portions being integral with one another. 